Enhanced electrical conductivity of poly(methyl methacrylate)-quasi-block-polystyrene/multiwalled carbon nanotubes composites with an optimized double percolation mechanism

We synthesized poly(methyl methacrylate)-quasi-block-polystyrene (PMMA-qb-PS) using a two step method of prepolymerization-copolymerization and incorporated multiwalled carbon nanotubes (MWNTs) to obtain conductive quasi-block (qb) copolymer/MWNTs composites. A superior conductivity of the qb copolymer/MWNTs composite at a weight ratio (MMA : St) of 1 : 1 and a MWNTs weight percentage of 1.0% (1% qb1 : 1) was observed over all mass ratios of the two monomers, and among counterparts of three categories (polymer/MWNTs composites in a random copolymer, quasi-block copolymer and blends matrices). The materials were characterized with a Hall effect detector, SEM, FTIR, and XPS. The results showed that the conductivity enhancement of 1% qb1 : 1 depended primarily on increasing the carrier concentration with most potent doping effect among the three categories. We proposed an optimized double percolation conductive mechanism in 1% "qb1 : 1 based on the present double-percolation theory of immiscible blends/MWNTs composites: "smashing" the large blocks of immiscible polymers into micro- and nano-scaled ones, thus increasing the degree of disorder among the two kinds of blocks and reducing the size of blocks for ameliorated percolation of carbon nanotube networks, which enabled a more potent doping effect of carbon nanotubes in the matrix and the enhancement of carrier concentration and therefore the conductivity.